3 use rustc_data_structures::fingerprint::Fingerprint;
4 use rustc_hir::def::{CtorKind, CtorOf};
5 use rustc_index::vec::Idx;
6 use rustc_middle::ty::ParameterizedOverTcx;
7 use rustc_serialize::opaque::FileEncoder;
8 use rustc_serialize::Encoder as _;
9 use rustc_span::hygiene::MacroKind;
10 use std::convert::TryInto;
11 use std::marker::PhantomData;
12 use std::num::NonZeroUsize;
14 /// Helper trait, for encoding to, and decoding from, a fixed number of bytes.
15 /// Used mainly for Lazy positions and lengths.
16 /// Unchecked invariant: `Self::default()` should encode as `[0; BYTE_LEN]`,
17 /// but this has no impact on safety.
18 pub(super) trait FixedSizeEncoding: Default {
19 /// This should be `[u8; BYTE_LEN]`;
22 fn from_bytes(b: &Self::ByteArray) -> Self;
23 fn write_to_bytes(self, b: &mut Self::ByteArray);
26 impl FixedSizeEncoding for u32 {
27 type ByteArray = [u8; 4];
30 fn from_bytes(b: &[u8; 4]) -> Self {
31 Self::from_le_bytes(*b)
35 fn write_to_bytes(self, b: &mut [u8; 4]) {
36 *b = self.to_le_bytes();
40 macro_rules! fixed_size_enum {
41 ($ty:ty { $(($($pat:tt)*))* }) => {
42 impl FixedSizeEncoding for Option<$ty> {
43 type ByteArray = [u8;1];
46 fn from_bytes(b: &[u8;1]) -> Self {
52 $(${index()} => Some($($pat)*),)*
53 _ => panic!("Unexpected {} code: {:?}", stringify!($ty), b[0]),
58 fn write_to_bytes(self, b: &mut [u8;1]) {
62 $(Some($($pat)*) => 1 + ${index()},)*
99 ( Static(ast::Mutability::Not) )
100 ( Static(ast::Mutability::Mut) )
101 ( Ctor(CtorOf::Struct, CtorKind::Fn) )
102 ( Ctor(CtorOf::Struct, CtorKind::Const) )
103 ( Ctor(CtorOf::Struct, CtorKind::Fictive) )
104 ( Ctor(CtorOf::Variant, CtorKind::Fn) )
105 ( Ctor(CtorOf::Variant, CtorKind::Const) )
106 ( Ctor(CtorOf::Variant, CtorKind::Fictive) )
107 ( Macro(MacroKind::Bang) )
108 ( Macro(MacroKind::Attr) )
109 ( Macro(MacroKind::Derive) )
131 ( Default { has_value: false } )
132 ( Default { has_value: true } )
144 ty::AssocItemContainer {
158 // We directly encode `DefPathHash` because a `LazyValue` would incur a 25% cost.
159 impl FixedSizeEncoding for Option<DefPathHash> {
160 type ByteArray = [u8; 16];
163 fn from_bytes(b: &[u8; 16]) -> Self {
164 Some(DefPathHash(Fingerprint::from_le_bytes(*b)))
168 fn write_to_bytes(self, b: &mut [u8; 16]) {
169 let Some(DefPathHash(fingerprint)) = self else {
170 panic!("Trying to encode absent DefPathHash.")
172 *b = fingerprint.to_le_bytes();
176 // We directly encode RawDefId because using a `LazyValue` would incur a 50% overhead in the worst case.
177 impl FixedSizeEncoding for Option<RawDefId> {
178 type ByteArray = [u8; 8];
181 fn from_bytes(b: &[u8; 8]) -> Self {
182 let krate = u32::from_le_bytes(b[0..4].try_into().unwrap());
183 let index = u32::from_le_bytes(b[4..8].try_into().unwrap());
187 Some(RawDefId { krate: krate - 1, index })
191 fn write_to_bytes(self, b: &mut [u8; 8]) {
194 Some(RawDefId { krate, index }) => {
195 // CrateNum is less than `CrateNum::MAX_AS_U32`.
196 debug_assert!(krate < u32::MAX);
197 b[0..4].copy_from_slice(&(1 + krate).to_le_bytes());
198 b[4..8].copy_from_slice(&index.to_le_bytes());
204 impl FixedSizeEncoding for Option<()> {
205 type ByteArray = [u8; 1];
208 fn from_bytes(b: &[u8; 1]) -> Self {
209 (b[0] != 0).then(|| ())
213 fn write_to_bytes(self, b: &mut [u8; 1]) {
214 b[0] = self.is_some() as u8
218 // NOTE(eddyb) there could be an impl for `usize`, which would enable a more
219 // generic `LazyValue<T>` impl, but in the general case we might not need / want
220 // to fit every `usize` in `u32`.
221 impl<T> FixedSizeEncoding for Option<LazyValue<T>> {
222 type ByteArray = [u8; 4];
225 fn from_bytes(b: &[u8; 4]) -> Self {
226 let position = NonZeroUsize::new(u32::from_bytes(b) as usize)?;
227 Some(LazyValue::from_position(position))
231 fn write_to_bytes(self, b: &mut [u8; 4]) {
232 let position = self.map_or(0, |lazy| lazy.position.get());
233 let position: u32 = position.try_into().unwrap();
234 position.write_to_bytes(b)
238 impl<T> FixedSizeEncoding for Option<LazyArray<T>> {
239 type ByteArray = [u8; 8];
242 fn from_bytes(b: &[u8; 8]) -> Self {
243 let ([ref position_bytes, ref meta_bytes],[])= b.as_chunks::<4>() else { panic!() };
244 let position = NonZeroUsize::new(u32::from_bytes(position_bytes) as usize)?;
245 let len = u32::from_bytes(meta_bytes) as usize;
246 Some(LazyArray::from_position_and_num_elems(position, len))
250 fn write_to_bytes(self, b: &mut [u8; 8]) {
251 let ([ref mut position_bytes, ref mut meta_bytes],[])= b.as_chunks_mut::<4>() else { panic!() };
253 let position = self.map_or(0, |lazy| lazy.position.get());
254 let position: u32 = position.try_into().unwrap();
255 position.write_to_bytes(position_bytes);
257 let len = self.map_or(0, |lazy| lazy.num_elems);
258 let len: u32 = len.try_into().unwrap();
259 len.write_to_bytes(meta_bytes);
263 /// Helper for constructing a table's serialization (also see `Table`).
264 pub(super) struct TableBuilder<I: Idx, T>
266 Option<T>: FixedSizeEncoding,
268 blocks: IndexVec<I, <Option<T> as FixedSizeEncoding>::ByteArray>,
269 _marker: PhantomData<T>,
272 impl<I: Idx, T> Default for TableBuilder<I, T>
274 Option<T>: FixedSizeEncoding,
276 fn default() -> Self {
277 TableBuilder { blocks: Default::default(), _marker: PhantomData }
281 impl<I: Idx, T> TableBuilder<I, T>
283 Option<T>: FixedSizeEncoding,
285 pub(crate) fn set<const N: usize>(&mut self, i: I, value: T)
287 Option<T>: FixedSizeEncoding<ByteArray = [u8; N]>,
289 // FIXME(eddyb) investigate more compact encodings for sparse tables.
290 // On the PR @michaelwoerister mentioned:
291 // > Space requirements could perhaps be optimized by using the HAMT `popcnt`
292 // > trick (i.e. divide things into buckets of 32 or 64 items and then
293 // > store bit-masks of which item in each bucket is actually serialized).
294 self.blocks.ensure_contains_elem(i, || [0; N]);
295 Some(value).write_to_bytes(&mut self.blocks[i]);
298 pub(crate) fn encode<const N: usize>(&self, buf: &mut FileEncoder) -> LazyTable<I, T>
300 Option<T>: FixedSizeEncoding<ByteArray = [u8; N]>,
302 let pos = buf.position();
303 for block in &self.blocks {
304 buf.emit_raw_bytes(block);
306 let num_bytes = self.blocks.len() * N;
307 LazyTable::from_position_and_encoded_size(
308 NonZeroUsize::new(pos as usize).unwrap(),
314 impl<I: Idx, T: ParameterizedOverTcx> LazyTable<I, T>
316 Option<T>: FixedSizeEncoding,
318 /// Given the metadata, extract out the value at a particular index (if any).
320 pub(super) fn get<'a, 'tcx, M: Metadata<'a, 'tcx>, const N: usize>(
324 ) -> Option<T::Value<'tcx>>
326 Option<T::Value<'tcx>>: FixedSizeEncoding<ByteArray = [u8; N]>,
328 debug!("LazyTable::lookup: index={:?} len={:?}", i, self.encoded_size);
330 let start = self.position.get();
331 let bytes = &metadata.blob()[start..start + self.encoded_size];
332 let (bytes, []) = bytes.as_chunks::<N>() else { panic!() };
333 let bytes = bytes.get(i.index())?;
334 FixedSizeEncoding::from_bytes(bytes)
337 /// Size of the table in entries, including possible gaps.
338 pub(super) fn size<const N: usize>(&self) -> usize
340 for<'tcx> Option<T::Value<'tcx>>: FixedSizeEncoding<ByteArray = [u8; N]>,
342 self.encoded_size / N